Oh, don't do that, unless you've specifically installed a Portable Install on both systems.
Instead, launch the MC17 on computer B, and use Media Server to initiate playback on Computer A.
In MC A
Tools > Options > Media Network >
- Use Media Network to share this library and enable DLNA
- Access Key (will make connecting easier for you)
- Authentication (enter a user name/password of your choice)
Leave MC A running.
In MC B
Same thing, but use the same username/password you set on MC A
Also set - Show playback zones from the server on the client
Now, in MC B, you can select MC A's library (Playing Now > Playing from <select MC A's library under here), and select the "zone" you want for playback. Send your tracks there (Right Click > Send To > <MC A's zone>. There are lots of ways to simplify playback this way, but let's start here.
See Also:
http://wiki.jriver.com/index.php/Library_Server